Manual transmissions and transaxles are shifted by shift fork assemblies. A shift fork assembly includes a shift fork that rides in a groove cut into a sliding clutch collar of the transmission or transaxle. One type of shift fork assembly includes a single shift shaft having multiple shift forks positioned thereon. The shift shaft is connected to the shift stick within the vehicle. Lateral or side-to-side movement of the is shift stick adjusts the angular position of the shift shaft. The shift shaft angular position determines which one of the shift forks moves with the shift shaft when the shift stick is moved into gear.
Another type of shift fork assembly includes a shift rail having a fixed shift fork that moves with the shift rail. Movement of the vehicle shift stick allows selection of a particular shift rail from a plurality of different shift rails. The shift fork on the selected shift rail moves with the selected shift rail when the shift stick is moved into gear. Because the shift fork is fixed to the shift rail, this type of shift fork assembly may be shifted remotely, for example, using valves and pistons.
Some transmissions and transaxles utilize both types of shift fork assemblies in the same transmission or transaxle. For example, compound vehicular transmissions have a main section connected in series with an auxiliary section. Typically, the main section is shifted directly with a shift stick connected to a single shift shaft, while the auxiliary section, whether a range section, splitter section, or combined range/splitter section, is shifted remotely using one or more valves and pistons. Thus, the auxiliary section of the transmission, for example, may employ a shift fork assembly of the type in which a shift fork is fixed to a shift rail. An auxiliary section ratio change may be indicated by the position of the shift stick, or may be initiated by a separate switch on the shift stick, such as a hi/lo range switch and/or a hi/lo splitter switch.
While shift fork assemblies of the type in which a shift fork is fixed to a shift rail are suitable for a number of applications which have been commercially successful, assembly of the shift fork to the shift rail is difficult. Typically the shift rail is positioned through an axial bore in the shift fork, and the shift rail and shift fork are placed inside the transmission (or transaxle) housing. Thereafter, a cone point screw is inserted into a shift fork mount hole intersecting the shift fork axial bore. The assembler aligns the shift fork mount hole with a transverse bore that extends partially into the shift rail, and then tightens the cone point screw, typically with a power tool. Due to space constraints when working on a partially assembled transmission (or transaxle), it is very difficult to tighten the cone screw. Further, many times the assembler does not know if the shift rail transverse bore and shift fork mount hole are aligned correctly until an attempt is made to tighten the cone screw. As such, it may take several assembly attempts before the shift fork is properly secured to the shift rail. With each shift fork to shift rail assembly potentially taking several attempts before proper assembly, the cost of manufacturing transmissions is increased.